Pulp screens remove contaminants from pulp suspensions and are critical to the production of high-quality paper products. Screen performance is determined by two internal components: a cylinder with apertures that pass acceptable fibres and block oversize contaminants, and a rotor that clears the apertures of any blockages. Capacity is an essential parameter of screen operation and a necessary consideration in evaluating changes made to enhance debris removal or reduce power consumption. The present study uses a pilot pulp screen to assess capacity limits, and a specialized laboratory screen with a-high-speed video camera to study what happens at a screen aperture.
What results is an understanding of some mechanisms related to the deposition and removal of fibres at an aperture where there is a time- varying ow bifurcation, and which is proposed herein as the essence of screen capacity.